Renewable energy sources: biomass, biofuels
In this post we face an issue which happen to hear about it as a viable alternative energy in different fields of application in relation to "traditional" solutions (based on fossil fuels), or Biomass.
But biomass what they are, how they are used and what potential they have? ... To all these questions will be answered later in the post.
WHAT ARE THE BIOMASS
The biomasses are organic materials of biological nature produced from animal or vegetable sources not fossilized, the use of which in the energy field consists in their use in the form of fuel, in substitution (or addition) of fuels of fossil nature, such as hydrocarbons, coal and natural gas.
The validity of biomass as fuel resides in their content of carbon and hydrogen, similarly to fossil fuels, always related to a compound of type carbon-hydrogen secondary more other molecules.
Regarding biomass from plant sources is produced to CO2 emission globally nothing because the carbon dioxide emitted is the same that had absorbed the plant to grow.
From the fermentation of some plants instead, such as sugar cane or other, it is possible to derive biofuels, in particular is possible to obtain high octane fuels (alcohols) for use in engines "gasoline" and similar fuels to diesel fuel for diesel engines (biodiesel ), and of course all the applications where fossil fuels are used.
FEATURES ENERGY
In terms of the energy characteristics there is a great variety of calorific values, especially as regards the use of plant biomass used "as is" (after trituration and eventual drying) as the calorific value depend on the type of wood used and by ' residual moisture in it.
As an example we can consider the calorific value of the pellets trade is around 16 MJ / kg, while for diesel the same parameter is 42MJ/kg.
This means that to achieve the same thermal power requires a higher consumption of pellets by a factor of approximately 2.5 times compared to diesel.
Regarding the ethanol, the calorific value is about 40% lower than that of a gasoline, but it has an octane rating higher than the latter, and therefore use in a motor on the one hand increased consumption by the necessity of a mixture of air - fuel richer in ethanol compared to gasoline, while on the other it makes possible the use of higher compression ratios with benefits on the performance of the same engine.
A comparison between diesel and biodiesel instead presents values of the calorific quite similar, even if the characteristics of the two fuels require some attention and optimization for power come exploited at best.
ADVANTAGES AND PROBLEMS OF BIOMASS
The biomasses have known a great development for a combination of various factors, first of all the scarcity of fossil fuels and the consequent (albeit influenced by speculation) an increase of the oil price, secondly by a greater awareness (albeit too often influenced by false ambientalismi and "prophets green") to environmental issues.
The use of waste and joinery cleaning of undergrowth (as regards the biomass derived from wood), as well as the use of the excess production of plantations such as sugar cane, for example (as regards biofuels) has provided in the source material for the production of the raw material, but the growing demand for increasingly pushes the economic system to produce the biomass specifically through the creation of areas intended for the production of the same.
This process has made it clear, especially with regard to the plantations intended for biofuels, the criticality of this resource as to pursue the business of biofuels, it was decided to subtract the ground for normal agricultural use for food, with a consequent increase in the prices of primary resources such as grain and cereals in general, making it even more precarious sustainability of the underdeveloped countries that converted their lands to such use.
24/05/2010
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Translated via software
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Source:
Italian version of ReteIngegneri.it